emacs/m4/lstat.m4

# serial 23

# Copyright (C) 1997-2001, 2003-2011 Free Software Foundation, Inc.
#
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.

dnl From Jim Meyering.

AC_DEFUN([gl_FUNC_LSTAT],
[
  AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
  dnl If lstat does not exist, the replacement <sys/stat.h> does
  dnl "#define lstat stat", and lstat.c is a no-op.
  AC_CHECK_FUNCS_ONCE([lstat])
  if test $ac_cv_func_lstat = yes; then
    AC_REQUIRE([gl_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK])
    if test $gl_cv_func_lstat_dereferences_slashed_symlink = no; then
      REPLACE_LSTAT=1
    fi
  else
    HAVE_LSTAT=0
  fi
])

# Prerequisites of lib/lstat.c.
AC_DEFUN([gl_PREREQ_LSTAT],
[
  AC_REQUIRE([AC_C_INLINE])
  :
])

AC_DEFUN([gl_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK],
[
  dnl We don't use AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK any more, because it
  dnl is no longer maintained in Autoconf and because it invokes AC_LIBOBJ.
  AC_CACHE_CHECK([whether lstat correctly handles trailing slash],
    [gl_cv_func_lstat_dereferences_slashed_symlink],
    [rm -f conftest.sym conftest.file
     echo >conftest.file
     if test "$as_ln_s" = "ln -s" && ln -s conftest.file conftest.sym; then
       AC_RUN_IFELSE(
         [AC_LANG_PROGRAM(
            [AC_INCLUDES_DEFAULT],
            [[struct stat sbuf;
              /* Linux will dereference the symlink and fail, as required by
                 POSIX.  That is better in the sense that it means we will not
                 have to compile and use the lstat wrapper.  */
              return lstat ("conftest.sym/", &sbuf) == 0;
            ]])],
         [gl_cv_func_lstat_dereferences_slashed_symlink=yes],
         [gl_cv_func_lstat_dereferences_slashed_symlink=no],
         [# When cross-compiling, be pessimistic so we will end up using the
          # replacement version of lstat that checks for trailing slashes and
          # calls lstat a second time when necessary.
          gl_cv_func_lstat_dereferences_slashed_symlink=no
         ])
     else
       # If the 'ln -s' command failed, then we probably don't even
       # have an lstat function.
       gl_cv_func_lstat_dereferences_slashed_symlink=no
     fi
     rm -f conftest.sym conftest.file
    ])
  test $gl_cv_func_lstat_dereferences_slashed_symlink = yes &&
    AC_DEFINE_UNQUOTED([LSTAT_FOLLOWS_SLASHED_SYMLINK], [1],
      [Define to 1 if `lstat' dereferences a symlink specified
       with a trailing slash.])
])